The present invention relates to a battery pack composed of assembled single-cell secondary batteries and a battery pack group in which the battery packs are connected in series, parallel or series-parallel.
Conventionally, there has been known a battery pack having a plurality of single cells connected in series, parallel or series-parallel in order to obtain a large capacity secondary battery. In addition, the significance of the battery pack is being rediscovered in recent years along with the popularization of electric vehicles and hybrid vehicles.
JP 2003-151526 A discloses an assembled battery which is constituted by combining a plurality of secondary battery single cells, which is produced by connecting the secondary battery single cells by bus bars and then processing the connected cells so as to be housed in an external case, and which improves resistance to vibrations and impacts from the outside while ensuring ease of productivity of the assembled battery and ease of workability in joining the bus bars and the like.
JP 2003-7345 A discloses a lithium secondary battery in which a flat case is constituted with a lightweight exterior material like a laminate film having a gas barrier layer and resin layers respectively provided on both faces of the gas barrier layer; and the flat case housing a battery element having positive and negative electrodes is hermetically closed.
JP 2012-178271 A discloses a technique to reduce the weight of a battery pack by shortening a terminal connecting member used to connect a positive terminal of one secondary battery to a negative terminal of the other secondary battery or by removing the terminal connecting member.